WP_Site_Icon::get_post_metadata( null|array|string $value, int $post_id, string $meta_key, bool $single )

Source

File: wp-admin/includes/class-wp-site-icon.php

public function get_post_metadata( $value, $post_id, $meta_key, $single ) {
		if ( $single && '_wp_attachment_backup_sizes' === $meta_key ) {
			$site_icon_id = get_option( 'site_icon' );

			if ( $post_id == $site_icon_id ) {
				add_filter( 'intermediate_image_sizes', array( $this, 'intermediate_image_sizes' ) );
			}
		}

		return $value;
	}